1. Field of the Invention
The present invention relates to a cleaning unit, a slit coating apparatus having the cleaning unit, and a method of coating a substrate, more particularly to a cleaning unit enhancing efficiency of coating process, a slit coating apparatus having the cleaning unit, and a method of coating a substrate.
2. Description of the Related Art
In general, a photosensitive material is used for patterning a thin film that performs a special function. The photosensitive material chemically reacts on light. When the photosensitive material is not coated uniformly, deterioration occurs in next processes.
When the photosensitive material is coated thicker than a predetermined thickness on a thin film, the thin film is under-etched. When the photosensitive material is coated thinner than the predetermined thickness, the thin film is over-etched.
A spin coating method is widely used as a method of uniformly coating the substrate with the photosensitive material. According to the spin coating method, the photosensitive material is dropped on a substrate, while the substrate is rotated rapidly. Therefore, the photosensitive material is spread on the substrate. However, the spin coating method is not preferable in order that the substrate of a liquid crystal display panel is coated with the photosensitive material, because the substrate of the liquid crystal display device is heavy and large. When the substrate of the liquid crystal display device is heavy and large, rotating the substrate is hard, and the substrate is damaged (or broken) easily.
Therefore, a slit coating method is introduced recently so as to coat the substrate of the liquid crystal display device with the photosensitive material. According to the slit coating method, the photosensitive material is provided to the substrate via a slit.
A slit coater for coating the substrate includes the slit. A length of the slit is substantially equal to a width of the substrate that is coated with the photosensitive layer. A width of the slit is substantially equal to a thickness of the photosensitive layer with which the substrate is coated. The slit coater discharges the photosensitive material via the slit having definite width. Therefore, the slit coater coats the substrate with the photosensitive material, while moving in a longitudinal direction of the substrate. Therefore, the substrate is coated with the photosensitive material by uniform thickness.
However, when the slit coater repeats coating operation, dregs are attached on the slit nozzle of the spin coater, so that a uniformity of a photosensitive layer formed on the substrate is deteriorated. As a result, a display quality of the liquid crystal display device is deteriorated.